Electricity and Galvanism. 125 



nitric acid is undergoing decomposition. The result is, that the elec- 

 tricity of the decomposing atoms is resolved into its two elements, 

 the negative fluid being impelled towards my right hand, and the 

 positive towards my left ; and, if the two ends of the series of pla- 

 tinum and zinc plates are connected by these wires, the separated 

 elements unite, and equilibrium is restored. With these separated 

 fluids I can produce remarkable effects, depending upon the energy 

 with which their union occurs. I now allow their union to be effect- 

 ed by means of this piece of platinum wire, which becomes brilliantly 

 ignited, from the violence of the neutralisation or discharge of the 

 two fluids, being sufficient to set in active vibration the interstitial 

 ethereal elements of the platinum, and thus produce the phenomena 

 of heat and light you are now witnessing. I now allow the discharge 

 or union to take place between these fragments of carbon ; the in- 

 tense evolution of light well attests the violence with which the ether 

 is made to vibrate. Now I will compel the two elements to traverse 

 this water before they unite : so powerful is the influence of these 

 wondrous agents, that chemical affinity is annihilated, the water is 

 resolved into its elements, and torrents of oxygen and hydrogen are 

 evolved . Lastly, I have before me two bars of iron surrounded by 

 wire ; these are at present merely inert metal, possessing nothing 

 peculiar save in figure. Let us now compel the two fluids to traverse 

 the wire round these bars before they unite. In an instant the bars 

 assume new properties, becoming magnets of enormous power, rapid- 

 ly and violently attracting the iron ball suspended over them, and 

 seizing, with almost uncontrollable power, the bar of iron I now 

 present to them. 



I said that change of temperature is sufficient to disturb the 

 electric equilibrium of bodies. This is invariably true, and a single 

 illustration will, I hope, be regarded as sufficient. 



On the table before me is a large magnetic needle suspended on 

 a pivot ; some coils of insulated copper wire pass above and below 

 the bar, the apparatus being, indeed, the well-known galvanometer. 

 Here is a bar of the metal bismuth; and I will twist the terminations 

 of the wire coil round the ends of the bar. The needle remains at 

 rest ; no disturbance of electricity occurs. But observe what occurs 

 the instant the flame of a spirit-lamp comes in contact with one end 



